Dermatomyositis (dur-muh-toe-my-uh-SY-tis) is a condition in which swelling and irritation, called inflammation, attacks the body's tissues. Dermatomyositis causes muscle weakness and a skin rash.

The condition, also called an autoimmune condition, isn't common. It can affect adults and children. In adults, dermatomyositis most often happens in the late 40s to early 60s. In children, it most often appears at ages 5 to 15.

There's no cure for dermatomyositis. But treatment can improve muscle strength and help muscles work better. Treatment also can help clear the skin rash.

The symptoms of dermatomyositis can appear at once or they can come on over time. The most common symptoms include:

• Skin changes. A violet-colored or dusky red rash appears, most often on the face and eyelids and on the knuckles, elbows, knees, chest and back. The rash may be harder to see on Black skin or brown skin.

  The rash is often the first sign of dermatomyositis. It may hurt and itch. There also may be small bumps on the hands, mainly near the knuckles.

  Children also may get white spots on their skin from calcium deposits, called calcinosis.

• Muscle weakness. Muscle weakness involves the muscles closest to the center of the body, called the trunk. This includes the muscles in the hips, thighs, shoulders, upper arms and neck. The weakness affects both the left and right sides of the body. It tends to get worse over time.

Some people with dermatomyositis have only the skin symptoms. But muscle weakness may start years later.

You're likely to first see your family doctor, who might refer you to a doctor who specializes in the treatment of arthritis and other diseases of the joints, muscles and bones (rheumatologist) and to a doctor who specializes skin diseases (dermatologist).

What you can do

Make a list that includes:

• Detailed descriptions of your symptoms and when they began
• Information about medical problems you've had, and those of your parents or siblings
• All the medications and dietary supplements you take and their doses
• Questions to ask the doctor

Take a family member or friend along, if possible, to help you remember the information you're given.

For dermatomyositis, questions to ask your doctor include:

• What is likely causing my symptoms?
• What are other possible causes?
• Are my symptoms likely to change over time?
• What tests might I need? Are special preparations required?
• Are treatments available for my condition? What treatments do you recommend?
• I have other medical conditions. How can I best manage them together?
• Do you have brochures or other printed material I can have? What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your doctor will likely ask you questions, such as:

• Did your condition develop gradually or come on suddenly?
• Are you easily fatigued during waking hours?
• Does your condition limit your activities?
• Has anyone in your family been diagnosed with a condition that affects the muscles?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?

Make an appointment with a healthcare professional if you get muscle weakness or a rash with no known cause.

Experts don't know the exact cause of dermatomyositis. Having certain gene changes may make people more likely to get the condition.

People assigned female at birth have a higher risk of dermatomyositis than do people assigned male at birth.

Possible complications of dermatomyositis include:

• Trouble swallowing. The condition may affect the muscles in the tube that carries food from the throat to the stomach, called the esophagus. This can lead to trouble swallowing, called dysphagia. Trouble swallowing may cause weight loss and not getting enough nutrition.
• Aspiration pneumonia. Trouble swallowing also may cause breathing food or liquids, including saliva, into the lungs. This is called aspiration and can lead to pneumonia.
• Breathing problems. Dermatomyositis may affect the chest muscles. This can cause breathing issues, such as shortness of breath. If breathing is affected enough, it can cause failure of the system that allows breathing, called respiratory failure.
• Calcium deposits. These can happen in the muscles, skin and connective tissues as the disease gets worse. These deposits are more common in children with dermatomyositis.

Linked conditions

Dermatomyositis might cause other conditions or raise the risk of getting them, including:

• Raynaud's disease. This condition causes the fingers, toes, cheeks, nose and ears to turn pale, purple or red in response to cold temperatures or stress. Color changes may be harder to see on Black skin or brown skin. The condition also may cause numbness and tingling.
• Other diseases. Other autoimmune conditions, such as lupus, rheumatoid arthritis, scleroderma and Sjogren syndrome, can happen with dermatomyositis.
• Cardiovascular disease. Dermatomyositis may cause the muscular walls of the heart to become inflamed, called myocarditis. A small number of people who have dermatomyositis may get congestive heart failure and irregular heart rhythms, called arrythmias.
• Lung disease. A condition called interstitial lung disease may happen with dermatomyositis. Interstitial lung disease is a group of conditions that cause scarring of lung tissue. Called fibrosis, the scarring makes lung tissue stiff and thick. This makes it hard for the lungs to expand and fill with air.
• Cancer. Dermatomyositis in adults has been linked to a higher risk of getting certain types of cancer. Ask your healthcare professional what cancer screenings you may need.

To diagnose dermatomyositis, a healthcare professional does a physical exam and checks muscle strength. The following tests may help with diagnosis:

• Blood tests. A blood test may show higher levels of muscle enzymes, which can mean muscle damage. A blood test also can detect autoantibodies linked with certain symptoms of dermatomyositis.
• Chest X-ray. This simple test can check for signs of the type of lung damage that may happen with dermatomyositis.
• Electromyography. For this test, a healthcare professional puts a thin needle electrode through the skin into the muscle. The test measures electrical activity of the muscles as they relax or tighten. Changes in the pattern of electrical activity can confirm a muscle disease. Testing different muscles can show which ones the condition affects.
• MRI. A magnetic field and radio waves from a computer make detailed pictures of the muscles. An MRI can find swelling and irritation, called inflammation, over a large area of affected muscle.

• Skin or muscle biopsy. A healthcare professional removes a small piece of skin or muscle to send to a lab for study. A skin sample can help confirm the diagnosis of dermatomyositis. A muscle biopsy can show muscle damage and swelling and irritation, called inflammation.

  If the skin biopsy confirms the diagnosis, a muscle biopsy might not be needed.

• Lung tests. A healthcare professional may suggest tests to see how well the lungs work and a CT of the chest. You may have these tests if you have certain autoantibodies that have been linked with a condition of lung scarring called interstitial lung disease that may happen with dermatomyositis.

There's no cure for dermatomyositis. But treatment can improve muscle strength and help the muscles work better. Treatment also can help the skin.

Medications

Medicines used to treat dermatomyositis include:

• Corticosteroids. Medicines such as prednisone can manage dermatomyositis symptoms well. But using these medicines over time can cause serious side effects, including muscle weakness. So your healthcare professional tapers the dosage little by little.
• Corticosteroid-sparing agents. When used with a corticosteroid, these medicines may allow for a lower dosage and fewer side effects of the corticosteroid. The two most common medicines for dermatomyositis are azathioprine (Azasan, Imuran) and methotrexate (Trexall, Xatmep).
• Medicines for more-serious illness. Other medicines that treat dermatomyositis include mycophenolate mofetil (Cellcept, Myhibbin) and rituximab (Rituxan). These medicines can lessen the need for long-term corticosteroids.
• Intravenous immunoglobulin. Also called IVIg, this purified blood product has healthy antibodies from thousands of blood donors. These healthy antibodies can block the antibodies that attack muscle in dermatomyositis.

  IVIg involves getting the medicine through a vein, called an infusion. IVIg treatments may be used regularly or sometimes. The treatment mainly helps with trouble swallowing.

• Antimalarial medicines. For an ongoing rash, a healthcare professional might prescribe this type of medicine, such as hydroxychloroquine (Plaquenil, Sovuna).

Therapy

Depending on how serious the symptoms are, treatment might include:

• Physical therapy. A physical therapist can show you exercises to improve your strength and tell you what level of activity is right for you.
• Speech therapy. If dermatomyositis weakens muscles used for swallowing, speech therapy can help you learn how to work with the weakness.
• Nutrition help. Over time, dermatomyositis can make it harder to chew and swallow. A registered dietitian can teach you how to make easy-to-eat foods that give you enough nutrition.

With dermatomyositis, places where the body has a rash are more sensitive to the sun. Protect your skin from the sun using sunscreen. Wear clothing and hats that protect from the sun.

Living with a chronic autoimmune disease can be a challenge. To help you cope, try the following:

• Know your illness. Read all you can about dermatomyositis and other muscle conditions. Talk to people who have a condition like yours. Ask your healthcare professional any questions that you have about your condition, diagnosis or treatment.
• Be a part of your medical team. Work with the healthcare professionals involved in your care. Follow your treatment plan, including physical therapy. Tell your healthcare team about any new symptoms you have.
• Know your limits. Ask for help when you need it. And let others know about the ways dermatomyositis limits you.
• Be active. Exercise can help you keep muscles strong. Ask your healthcare professional or physical therapist for a detailed plan before starting an exercise program.
• Rest when you're tired. Don't wait until you're worn out. Learn to pace yourself so that you keep your energy level, get done what you need to do and feel better mentally.
• Accept your feelings. Dealing with an ongoing illness may cause anger, sadness and other feelings. You might feel like your life is a challenge and that you're alone.

  Stay close to family and friends. Stick to your daily routine as best you can. Do things you enjoy. Many people find support groups helpful.

Start by seeing your main healthcare professional, who might send you to a specialist in conditions of the joints, muscles and bone, called a rheumatologist, and a specialist in conditions of the skin, called a dermatologist.

What you can do

Take a family member or friend along, if you can, to help you remember the advice you get.

Make a list of:

• Your symptoms, including when they began and which muscles are affected.
• Key personal information, including major stresses, recent life changes, and your and your family's medical history.
• All medicines, vitamins or other supplements you take, including the dosages.
• Questions to ask your healthcare professional.

For dermatomyositis, some questions to ask include:

• What is the likely cause of my symptoms?
• What are other possible causes for my symptoms?
• What tests do I need? Do I need to do anything to prepare for them?
• What treatments do you suggest?
• I have other medical conditions. How can I best manage them together?
• Do you have brochures or other printed material that I can have? What websites do you suggest?

Be sure to ask all the questions you have.

What to expect from your doctor

Your healthcare professional may ask you questions, such as:

• Did your symptoms come on slowly or did they start all at once?
• Do you easily tire during waking hours?
• What does your condition keep you from doing?
• Has anyone in your family been diagnosed with a condition that affects the muscles?
• What, if anything, seems to make your symptoms better?
• What, if anything, seems to make your symptoms worse?